The present invention relates to a mechanism for adjusting spring-loaded friction clutches of large automotive vehicles. In particular, this invention relates to a clutch adjuster that secures or locks-in the adjustment and prevents rotational movement between the adjusting ring and the gear of the clutch adjuster.
Most clutches used in heavy trucks contain some type of clutch adjuster in which a manually-operated rotary gear meshes with the internal teeth of the adjusting ring to accomplish the adjustment. The rotating gear typically includes a central bolt terminating in a hex-head that is engaged by a socket wrench for rotating the gear. The clutch adjuster is locked in position by a strap that prevents rotation of the head associated with the gear. The locking and unlocking of the clutch adjuster is done by moving or removing the lock strap, which requires of manipulation of the hold-down screws that secure the strap to the clutch housing. The hold-down screws are often difficult to access, thus complicating adjustment of the clutch with this type of clutch adjuster.
This drawback was addressed by the clutch adjusters shown in Flowtow et al. U.S. Pat. No. 4,953,680. The Flowtow et al. clutch adjusters are designed to unlock by pressing the center bolt down at a reasonable force (e.g., 15 lbs.). Specifically, axial movement of the center bolt is necessary to perform the locking and unlocking of the clutch adjuster. Due to the dirty environment and the size of the ring to be rotated, the teeth of the adjusting ring and clutch adjuster can become frozen or locked. This increases substantially the force needed to axially move the center bolt to unlock the adjuster, and may make it practically impossible. Further, in the commercial version (shown in FIG. 5), the locking is “blind,” i.e., the locking surfaces are obscured from view. This leads to uncertainty as to whether locking has, in fact, occurred. If the Flowtow et al. clutch adjuster is not, in fact, locked into position, upon the first engagement of the clutch, the central bolt will rotate, and damage the locking strap. This results in gross mis-adjustment of the clutch, and the requires that the clutch adjuster be replaced.
Therefore, it is an object of the present invention to provide a clutch adjuster in which manipulation of a lock strap and mounting screws is not required.
It is a further object to provide such a clutch adjuster that provides a visual indication that the adjuster is locked into position, thus offering safety and certainty in operation.